ADHD occurs in 3% to 5% of the US population.1 The risk for comorbidity is high, and the presence of comorbid disorders warrants special consideration in the treatment of patients with ADHD. For example, a comorbid diagnosis of ADHD and depression occurs in approximately 20% to 30% of patients, and ADHD and anxiety in more than 25% of patients.1

Comorbidity rates in adults are equal to or higher than those in children, although very few studies have examined these patterns over time in adults. A longitudinal study by Michielsen and colleagues1 assessed older adults over a 6-year period for symptoms of ADHD, depression, and anxiety: ADHD was associated with a higher risk for both depression and anxiety.

Some researchers propose that comorbid bipolar disorder (BD) and ADHD should form a separate clinical phenotype of BD. A recent study examined BD in patients with and without ADHD.2 Patients were screened for both BD and ADHD, as well as for mood, anxiety, eating, impulse control, alcohol, and substance use disorders. Approximately 20% of adults with BD also had ADHD. Patients with BD and ADHD had higher rates of current mixed episodes, lower rates of mania, greater impairment overall, and higher levels of depression. Patients with BD and ADHD also had lower remission rates and higher rates of substance use disorders, and they reported greater levels of familial maladjustment than adults with BP alone.

ADHD is associated with abnormalities in the frontal lobes. It makes sense that any neurological disorder that originates in these regions would increase the risk for ADHD. Zhang and colleagues3 evaluated children with frontal lobe epilepsy for the prevalence of ADHD: 89.4% of the children with an abnormal EEG had coexisting ADHD compared with only 25% of children with normal EEG readings. The authors concluded that frontal lobe epilepsy is strongly linked with the occurrence of ADHD, and this occurrence is even greater for individuals with an abnormal EEG.

It is important to treat all comorbidities. Because individuals with comorbid psychiatric disorders experience greater cognitive, social, and psychological impairments, however, mental health professionals are encouraged to screen for early detection and intervention.

This article was first posted online on 7/26/2013 and has since been updated.

Disclosures

Dr Sherman is a behavior therapist and school psychologist at the Tarnow Center for Self-Management in Houston. Dr Tarnow Associate Professor of Psychiatry and Pediatrics at Baylor College of Medicine, and Clinical Associate Professor at University of Texas Medical School-Houston. He is Director and Owner of the Tarnow Center for Self-Management in Houston. The authors report no conflicts of interest concerning the subject matter of this article.